1. Field of the Invention
The present invention relates to an apparatus and method for initializing a stepper motor, and more particularly to an apparatus and method for initializing a stepper motor for synchronizing a timing when a stopper piece linked with a rotor of the stepper motor is brought into contact with a fixed stopper with a reference step in an exciting signal for driving the stepper motor.
2. Description of the Related Art
In an in-vehiclemeter such as a speedmeter for indicating a vehicle speed, a tachometer for indicating an engine speed, etc., in recent years, a stepper motor has been used in order to satisfy the demand of response and indicating accuracy. However, in order to make an accurate indication using the stepper motor, initial synchronization must be previously acquired between the timing when a stopper piece interlocked with the rotation of the stepper motor is brought into contact with a fixed stopper and a reference step in an exciting signal for driving the stepper motor.
Generally, the above initial synchronization has been acquired in a step of assembling the in-vehicle meter. Traditionally, with a stopper piece (or pointer) linked with the rotor being pressed so that the stopper piece is in contact with the fixed stopper, the above reference step has been synchronized with the rotating pattern of the rotor at this time. Otherwise, the initializing has been carried out taking the amount of backlash into consideration.
However, the above traditional method presents a problem in that an index which is a guideline for initializing is not clear, the initializing is not stable under the influence of the material of the pointer, gear and other components of a motor and a play of the gear, and a long time is taken for the initializing.
An object of this invention is to provide an apparatus and method for initializing a stepper motor which can clarify an index of initializing by a digit to facilitate the initializing and shorten the time taken for the initializing.
In accordance with a first aspect of this invention, there is provided an apparatus for initializing a stepper motor comprising:
means for supplying an exciting signal to a coil for rotating a rotor of the stepper motor so as to shift a stopper piece linked with the rotor in a first rotating direction toward a zero point defined by a fixed stopper, the exciting signal having a single electric cycle composed of a plurality of exciting steps;
means for inputting a rebounding step number which is the exciting step when the rotor reverses its rotating direction from the first rotating direction from a second direction opposite thereto;
means for computing a shift step number shifted by the number of exciting steps which corresponds to a half of the single electric cycle from the rebounding step number; and
means for initializing the stepper motor so as to apply the exciting signal to the coil with the shift step number being synchronized with a timing when the stopper piece is brought into contact with the fixed stopper.
In this configuration, the index which is a guide line for initializing is clarified so that the initializing can be performed easily and surely. Therefore, in the process of motor assembling, the time for initializing can be greatly shortened, thus realizing the initializing with great accuracy.
Preferably, the means for initializing the stepper motor comprises means for storing data in a storage means connected to a motor driver for driving the stepper motor.
In this configuration, the time for initializing can be further shortened.
Preferably, the means for initializing the stepper motor comprises means for displaying the shift step number.
In this configuration, because the shift step number is displayed, it can be used to recognize the quality of the product during a motor assembling process. For example, it can be used to inspect whether or not the initialization has been completed appropriately.
Preferably, the apparatus for initializing a stepper motor comprises:
a plurality of stepper motors; and
means for aligning shift step numbers computed so as to correspond to the stepper motors on the corresponding data holding positions allotted to the storage means.
In this configuration, the shift step numbers corresponding to the stepper motors are aligned so as to the corresponding data storing positions allotted in the storage means. Therefore, the data can be simultaneously stored so that the time taken for initializing when the plurality of stepper motors are used, particularly the time taken for data storing can be shortened.
Preferably, the rotor is composed of five pairs of magnetic poles magnetized alternately and uniformly with an N-pole and an S-pole; and
the exciting signal is composed of 32 exciting steps which are created on the basis of a sine wave and uniformly allotted.
In this configuration, the rotor control can be made smoothly.
In accordance with the second aspect of this invention, there is provided a method for initializing a stepper motor comprising:
a first step of supplying an exciting signal to a coil for rotating a rotor of the stepper motor so as to shift a stopper piece linked with the rotor in a first rotating direction toward a zero point defined by a fixed stopper, the exciting signal having a single electric cycle composed of a plurality of exciting steps;
a second step of inputting a rebounding step number which is the exciting step when the rotor reverses its rotating direction from the first rotating direction from a second direction opposite thereto;
a third step of computing a shift step number shifted by the number of exciting steps which corresponds to a half of the single electric cycle from the rebounding step number; and
a fourth step of initializing the stepper motor so as to apply the exciting signal to the coil with the shift step number being synchronized with a timing when the stopper piece is brought into contact with the fixed stopper.
In this method, the index which is a guide line for initializing is clarified so that the initializing can be performed easily and surely. Therefore, in the process of motor assembling, the time for initializing can be greatly shortened, thus realizing the initializing with great accuracy.
In the above method, preferably, the fourth step comprises:
storing data in a storage means connected to a motor driver for driving the stepper motor.
In this method, the time for initializing can be further shortened.
Preferably, the above method further comprises a fifth step of displaying the shift step number.
In this method, since the shift step number is displayed, it can be used to recognize the quality of the product during a motor assembling process. For example, it can be used to inspect whether or not the initialization has been completed appropriately.
The above and other objects and features of the invention will be more apparent from the following description taken in conjunction with the accompanying drawings.